Radio access networks (RANs) provide for radio communication links to be arranged within the network between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘mobile stations.’ At least one other terminal, e.g. used in conjunction with mobile stations, may be a fixed terminal, e.g. a base station, eNodeB, repeater, and/or access point. Such a RAN typically includes a system infrastructure that generally includes a network of various fixed terminals, which are in direct radio communication with the mobile stations. Each of the fixed terminals operating in the RAN may have one or more transceivers which may, for example, serve mobile stations in a given region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The mobile stations that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal In one example, all radio communications to and from each mobile station within the RAN are made via respective serving fixed terminals. Sites of neighboring fixed terminals may be offset from one another and may be non-overlapping or partially or fully overlapping with one another.
RANs may operate according to an industry standard broadband protocol such as, for example, an open media alliance (OMA) push to talk (PTT) over cellular (OMA-PoC) standard, a voice over IP (VoIP) standard, or a PTT over IP (PoIP) standard. Typically, protocols such as PoC, VoIP, and PoIP are implemented over broadband RANs including third generation and fourth generation networks such as third generation partnership project (3GPP) Long Term Evolution (LTE) networks.
RANs may additionally or alternatively operate according to an industry standard land mobile radio (LMR) protocol such as, for example, the Project 25 (P25) standard defined by the Association of Public Safety Communications Officials International (APCO), or other radio protocols, the TETRA standard defined by the European Telecommunication Standards Institute (ETSI), the Digital Private Mobile Radio (dPMR) standard also defined by the ETSI, or the Digital Mobile Radio (DMR) standard also defined by the ETSI. Because these generally systems provide lower throughput than the 3GPP and LTE systems, they are sometimes designated narrowband RANs.
Communications in accordance with any one or more of these protocols or standards, or other protocols or standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), OFDMA (orthogonal frequency division multiplexing access), or CDMA (code division multiple access) protocols. Mobile stations in RANs such as those set forth above send and receive media data (encoded voice, audio, images, and/or video) and other types of data in accordance with the designated protocol.
OMA-PoC, in particular, enables familiar PTT and “instant on” features of traditional half duplex mobile stations, but uses mobile stations operating over modern cellular telecommunications networks. Using PoC, wireless mobile stations such as mobile telephones and notebook computers can function as PTT half-duplex mobile stations for transmitting and receiving auditory data. Other types of PTT models and multimedia call models (MMCMs) are also available.
Floor control in an OMA-PoC session is generally maintained by a PTT server that controls communications between two or more wireless mobile stations. When a user of one of the mobile stations keys a PTT button, a request for permission to speak in the OMA-PoC session is transmitted from the user's mobile station to the PTT server using, for example, a real-time transport protocol (RTP) message. If no other users are currently speaking in the PoC session, an acceptance message is transmitted back to the user's mobile station and the user can then speak into a microphone of the device. Using standard compression/decompression (codec) techniques, the media is digitized (if necessary) and transmitted using discrete data packets (e.g., together which form a stream over time), such as according to RTP and internet protocols (IP), to the PTT server. The PTT server then transmits the data packets to other users of the PoC session (e.g., to other mobile stations in the group of mobile stations or talkgroup to which the user is subscribed), using for example a unicast, point to multipoint, or broadcast communication technique.
Narrowband LMR systems, on the other hand, operate in either a conventional or trunked configuration. In either configuration, a plurality of mobile stations are partitioned into separate groups of mobile stations. In a conventional system, each mobile station in a group is selected to a particular frequency for communications associated with that mobile station's group. Thus, each group is served by one channel, and multiple groups may share the same single frequency (in which case, in some embodiments, group IDs may be present in the group data to distinguish between groups using the same shared frequency).
In contrast, a trunked radio system and its mobile stations use a pool of traffic channels for virtually an unlimited number of groups of mobile stations (e.g., talkgroups). Thus, all groups are served by all channels. The trunked radio system works to take advantage of the probability that not all groups need a traffic channel for communication at the same time. When a member of a group requests a call on a control channel (sometimes also identified as a rest channel) on which all of the mobile stations in the system idle awaiting new call notifications, in one embodiment, a call controller assigns a separate traffic channel for the requested group call, and all group members move from the assigned control channel to the assigned traffic channel for the group call. In another embodiment, when a member of a group requests a call on the control channel, the call controller may convert the control on which the mobile stations were idling to a traffic channel for the call, and instruct all mobile stations that are not participating in the new call to move to a newly assigned control channel selected from the pool of available channels. With a given number of channels, a much greater number of groups can be accommodated in a trunked system as compared with conventional radio systems.
Group calls may be made between wireless and/or wireline participants in accordance with either or both of a narrowband or a broadband protocol or standard. Group members for group calls may be statically or dynamically defined. That is, in a first example, a user or administrator working on behalf of the user may indicate to the switching and/or radio network (perhaps at a call controller, PTT server, zone controller, or mobile management entity (MME), base station controller (BSC), mobile switching center (MSC), site controller, Push-to-Talk controller, or other network device) a list of participants of a group at the time of the call or in advance of the call. The group members (e.g., mobile stations) could be provisioned in the network by the user or an agent, and then provided some form of group identity or identifier, for example. Then, at a future time, an originating user in a group may cause some signaling to be transmitted indicating that he or she wishes to establish a communication session (e.g., group call) with each of the pre-designated participants in the defined group. In another example, mobile stations may dynamically affiliate with a group (and also disassociate with the group) perhaps based on user input, and the switching and/or radio network may track group membership and route new group calls according to the current group membership.
One problem that has arisen with the increasing proliferation of wireless mobile stations and increasing number of separate groups of mobile stations in RANs is that a number of channels that can be supported at a single multicarrier base station remains limited by a power capacity of the power amplifier at the base station. As the number of carriers is increased, the power available to each channel decreases. Conversely, as the power used to transmit each channel is decreased, the number of carriers can be increased.
Further, the continued adoption of alternative energy, power-limited RANs that may contain one or more base stations powered by alternative energy sources such as solar or wind energy, places further limitations on power consumption in the RANs.
Accordingly, what is needed is an improved method and apparatus for adjusting base station transmit power in RANs so as to further reduce power consumption and/or increase the number of available carriers in the RANs.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.